Process for producing coated urea-formaldehyde polymers

ABSTRACT

The present invention relates to novel urea-formaldehyde polymers coated with an active ingredient, a method of making the same, and their use.

FIELD OF THE INVENTION

The present invention relates to urea-formaldehyde polymers. Moreparticularly the present invention relates to novel urea-formaldehydepolymers coated with an active ingredient, a method of making same, andtheir use.

BACKGROUND OF THE INVENTION

The industrial applicability of urea-formaldehyde polymers has beenknown from some time. These polymers find use in diverse applicationsfrom use in the agricultural industry to use as an additive in paper,paint, and varnish applications. In the paper industry, it is known thaturea-formaldehyde polymers can be used to improve opacity andprintability. However, in agricultural applications, theurea-formaldehyde polymers serve mainly as a carrier for an activeingredient. Typically, the active ingredient is deposited into thecavities and onto the surface of the urea-formaldehyde polymer bydissolving the active ingredient in a solvent, and spraying thissolution onto the surface of the urea-formaldehyde polymer in afluidized bed drier. The solvent is volatized by the hot air in thefluidized bed dryer, producing a urea-formaldehyde polymer coated withthe active ingredient.

However, the inventors hereof have discovered that some solventspresently used do not completely volatize, and the incompletevolatilization of the solvent limits the amount of active ingredientdeposited onto the urea-formaldehyde polymer carrier. In addition,fluidized bed driers are specialized pieces of equipment requiringextensive and expensive air handling and conditioning capabilities.Therefore, there is a need in the art for a process wherebyurea-formaldehyde polymer can be effectively coated with activeingredients.

SUMMARY OF THE INVENTION

The present invention relates to a process for depositing one or more,in some embodiments only one, active ingredients onto urea-formaldehydepolymers comprising contacting, in a drying device, a urea-formaldehydepolymer with a solution comprising a solvent selected from ethers,alcohols, hydrocarbons, halogenated hydrocarbons and aromatichydrocarbons and an active ingredient under conditions includingelevated temperatures and sub-atmospheric pressures.

In another embodiment, the present invention relates to a processcomprising adding to a drying device a urea-formaldehyde polymer, asolution comprising a solvent selected from ethers, alcohols,hydrocarbons, halogenated hydrocarbons and aromatic hydrocarbons, and anactive ingredient under temperatures effective at volatizing at least aportion of the solvent thus producing an active-ingredient-coatedurea-formaldehyde polymer.

In another embodiment, the present invention relates to aurea-formaldehyde polymer having deposited thereon greater than 35 wt.%, based on the weight of the urea-formaldehyde polymer, of an activeingredient.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention relates to a process fordepositing active ingredients onto urea-formaldehyde polymers. “Activeingredient” as used herein is meant to refer to compounds, chemicals,etc., that find use in agricultural applications and are commonlyapplied to urea-formaldehyde polymers. Non-limiting examples of activeingredients suitable for use herein include urease inhibitors,fungicides and insecticides. Urease inhibitor, as used herein, is meantto refer to compounds that interfere with urease activity and reduceurea hydrolysis in soils. In preferred embodiments the active ingredientis a urease inhibitor, more preferably N-n-butyl thiophosphoric triamide(“NBPT”).

Urea-formaldehyde polymers suitable for use herein can be selected fromany urea-formaldehyde polymers known, and these polymers can be made byany method known in the art. For example, the urea-formaldehyde polymersused herein can be made by the process taught in U.S. Pat. No.6,936,078, which is incorporated in its entirety herein by reference.Non-limiting examples of urea-formaldehyde polymers suitable for use inthe practice of the present include those sold under the name PERGOPAK®by the Albemarle Corporation. In preferred embodiments of the presentinvention, the urea-formaldehyde polymer is selected from those having awater content of between from about 1 and 80 wt. %, based on the weightof the urea-formaldehyde polymer. In more preferred embodiments, theurea-formaldehyde polymer is selected from those having a water contentof between from about 10 and 35 wt. %, based on the weight of theurea-formaldehyde polymer. In a most preferred embodiment, theurea-formaldehyde polymer is selected from those having a water contentof between from about 10 and 20 wt. %, based on the weight of theurea-formaldehyde polymer. Exemplary urea-formaldehyde polymers suitablefor use herein are those sold under the name PERGOPAK® by the AlbemarleCorporation, preferably the PERGOPAK® M line of urea-formaldehydepolymers.

The means by which the one or more active ingredients are deposited ontothe urea-formaldehyde polymer is not critical to the instant inventionand can be selected from any method known. Preferably the one or moreactive ingredients are deposited onto the urea-formaldehyde polymer byusing a drying device such as a high shear mixer, ribbon drier, bladedrier, or other similar device. Preferably the drying device is a ribbondrier or blade drier.

Typically, the one or more active ingredients are deposited onto theurea-formaldehyde polymer by introducing into the drying device aurea-formaldehyde polymer and a solution comprising a solvent and one ormore active ingredients, in some embodiments only one, as describedabove. Solvents suitable for use herein can be selected from anyvolatile organic solvent that can be solubilize the selected activeingredient. Non-limiting examples of suitable solvents include ethers,alcohols, hydrocarbons, halogenated hydrocarbons and aromatichydrocarbons. In preferred embodiments, the solvent is selected fromethers, alcohols and hydrocarbons. In more preferred embodiments, thesolvent is tetrahydrofuran (“THF”). The inventors hereof haveunexpectedly discovered that the use of these solvents allows thepractitioner to produce an active-ingredient-containingurea-formaldehyde polymer that has an active ingredient concentrationhigher than previously achievable. While not wishing to be bound bytheory, the inventors hereof believe this higher active ingredientconcentration is directly attributable to the solvent selected for twoimportant reasons. Firstly, urea-formaldehyde polymers are typicallycross-linked polymers that do not readily solubilize in typicalsolvents. However, some solvents currently used, most commonlyN-methyl-2-pyrrolidinone (“NMP”), in coating urea-formaldehyde polymersare strong enough to swell or partially dissolve the urea-formaldehydepolymers, thus limiting the ability to deposit the active ingredientonto the urea-formaldehyde polymer. Secondly, some solvents currentlyused do not completely volatize in the processes used to deposit theactive ingredient onto the urea-formaldehyde polymers. The incompletevolatilization of the solvent leads to a portion of theurea-formaldehyde polymer being coated with solvent, again limiting thesurface area onto which the active ingredient can be deposited.

The solution comprising the one or more active ingredients typicallycontains from about 50 to about 80 wt. %, based on the weight of thesolution, of the one or more active ingredient(s). In preferredembodiment, the solution comprises from about 60 to 70 wt. %, based onthe weight of the solution, of the one or more active ingredient(s). Ina particularly preferred embodiment, the solution comprises from about62 to about 68 wt. %, based on the weight of the solution, of the one ormore active ingredient(s).

In the practice of this embodiment of the present invention, theurea-formaldehyde polymer and solution can be introduced into the dryingdevice simultaneously, in stages, either the polymer or solutionintroduced before the other, or any combinations thereof. Thus, thisembodiment of the present invention can be either a batch or continuousprocess. In preferred embodiments, the solution is introduced into thedrying device after the urea-formaldehyde polymer. In this and otherembodiments, the introduction of the solution is controlled to avoidover-wetting of the urea-formaldehyde polymer. The inventors hereof havediscovered that over-wetting can be prevented by introducing thesolution into the drying device at a rate substantially equal to therate at which the solvent volatilizes. The volatilization of the solventis achieved by operating the drying device under conditions that includeelevated temperatures; preferably the drying device is operated underelevated temperatures and sub-atmospheric pressures. Elevatedtemperatures, as used herein, is meant to refer to temperatureseffective at volatilizing at least a portion, preferably substantiallyall, of the selected solvent, i.e. temperatures above the boiling pointof the selected solvent. Preferably the temperatures under which thedrying device is operated are in the range of from about 20° C. to about200° C., more preferably in the range of from about 20° C. to about 100°C., most preferably from about 20° C. to about 50° C. Also, as statedabove, it is preferred that the drying device be operated undersub-atmospheric pressures, i.e. under a vacuum. These pressures arepreferably in the range of from about 760 mmHg to about 0.1 mmHg, morepreferably in the range of from about 500 mmHg to about 50 mmHg, mostpreferably from about 100 mmHg to about 50 mmHg.

Through the use of the presently disclosed coating process,active-ingredient-coated urea-formaldehyde polymers that arecharacterized as having an active ingredient concentration superior tothose currently available can be produced. Typically theactive-ingredient-coated urea-formaldehyde polymers according to thepresent invention have an active ingredient concentration greater thanabout 35 wt. %, based on the weight of the active-ingredient-coatedurea-formaldehyde polymer. Preferably the active ingredientconcentration is in the range of from about 40 wt. % to about 80 wt. %,on the same basis. More preferably the active ingredient concentrationis in the range of from about 50 wt. % to about 70 wt. %, on the samebasis.

The inventors hereof have also discovered that active-ingredient-coatedurea-formaldehyde polymers produced by the present invention have astorage life superior to those made using other solvents such as NMP,thus making the active-ingredient-coated urea-formaldehyde polymers moresuitable for use in agricultural applications wherein the function of aurease inhibitor is desired. The storage life of theactive-ingredient-coated urea-formaldehyde polymers refers to the lossof active ingredient over time, and is thus an important quality. Longerstorage life indicates that the active-ingredient-coatedurea-formaldehyde polymers retain the active ingredient for a longerperiod of time under normal storage conditions. In preferredembodiments, the storage life of the present active-ingredient-coatedurea-formaldehyde polymers is at least twice that ofactive-ingredient-coated urea-formaldehyde polymers that were coatedusing NMP as a solvent.

The above description is directed to several embodiments of the presentinvention. Those skilled in the art will recognize that otherembodiments, which are equally effective, could be devised for carryingout the spirit of this invention. The following examples will illustratethe present invention, but are not meant to be limiting in any manner.

EXAMPLES Example 1 Pergopak® M Loading Using a 45.7 wt. % Solution ofNBPT (N-n-butylthiophosphoric Triamide) in NMP (n-methylpyrrolidinone)

Inside a fume hood 35.1 grams of Pergopak® M, a urea formaldehydepolymer commercially available from the Albemarle® Corporation, wasweighed into a stainless steel mixing bowl. Into a 250 ml additionfunnel was weighed 88.0 grams of the 45.7 wt. % solution of NBPT in NMP.A section of Tygon® tubing and a plastic pipette were added to theadditional funnel to allow for the drop wise addition of the NBPTsolution onto the Pergopak® M. The mixer was turn on to speed setting#1. The NBPT solution was added to the solid Pergopak® M over a10-minute period. After the addition was complete the weight of thecontents of the mixing bowl was determined to be 117.3 grams. Another6.0 grams of the NBPT in NMP solution was added over a 10-minute periodvia the addition funnel. The mixture was stirred for an additional 20minutes at mixer speed setting #2. The final weight of Pergopak® Mloaded with the NBPT solution was 124.3 grams of an off whitecompactable solid.

Example 2 Pergopak® M Loading Using a 45.7 wt. % Solution of NBPT(N-n-butylthiophosphoric Triamide) in NMP (n-methylpyrrolidinone)

Inside a fume hood 35.4 grams of Pergopak® M was weighed into astainless steel mixing bowl. Into a 250 ml beaker was weighed 70.6 gramsof the 45.7 wt. % solution of NBPT in NMP. The mixer was turn on tospeed setting #1. The NBPT solution was added to the solid Pergopak® Musing a plastic pipette over a 37-minute period. When approximately halfof the NBPT solution was added the mixer speed was increased to setting#2. The mixture was stirred for an additional 10 minutes at mixer speedsetting #7. The final weight of Pergopak® M loaded with the NBPTsolution was 105.0 grams of an off white compactable solid.

Example 3 Pergopak® M Loading Using a 45.7 wt. % Solution of NBPT(N-n-butylthiophosphoric Triamide) in NMP (n-methylpyrrolidinone)

Inside a fume hood 35.6 grams of Pergopak® M was weighed into astainless steel mixing bowl. Into a 250 ml beaker was weighed 97.7 gramsof the 45.7 wt. % solution of NBPT in NMP. The mixer was turn on tospeed setting #1. The NBPT solution was added to the solid Pergopak® Musing a plastic pipette over a 40-minute period. When approximately 30%of the NBPT solution had been added the mixer speed was increased tosetting #2. When approximately 80% of the NBPT solution had been addedthe solid in the mixing bowl took on a wet appearance and the mixerspeed was increased to setting #3. After all of the NBPT solution hadbeen added the mixture was stirred for an additional 11 minutes at mixerspeed setting #7. The final weight of Pergopak® M loaded with the NBPTsolution was 132.0 grams of an off white compactable solid with a wettedappearance.

Example 4 Pergopak® M Loading Using a 45.8 wt. % Solution of NBPT(N-n-butylthiophosphoric Triamide) in THF (Tetrahydrofuran)

Inside a fume hood 35.7 grams of Pergopak® M was weighed into astainless steel mixing bowl. Into a 250 ml addition funnel was weighed157.5 grams of the 45.8 wt. % solution of NBPT in THF. A section ofTygon® tubing was added to the additional funnel to allow for the dropwise addition of the NBPT solution onto the Pergopak® M. The mixer wasturn on to speed setting #1. The NBPT solution was added to the solidPergopak® M over a 46-minute period. The bowl was rotated by hand duringthe addition of the NBPT solution to facilitate mixing. The mixture wasstirred for an additional 49 minutes and during the last 10 minutes ofmixing the mixer speed was increased to setting #6 to break up lumps.The final weight of Pergopak® M loaded with the NBPT solution was 107grams of a fine white free flowing powder.

Example 5 Pergopak® M Loading Using a 45.8 wt. % Solution of NBPT(N-n-butylthiophosphoric Triamide) in THF (Tetrahydrofuran)

Inside a fume hood 25.7 grams of Pergopak® M was weighed into astainless steel mixing bowl. Into a 250 ml addition funnel was weighed126.2 grams of the 45.8 wt. % solution of NBPT in THF. A section ofTygon® tubing was added to the additional funnel to allow for the dropwise addition of the NBPT solution onto the Pergopak® M. The mixer wasturn on to speed setting # 1. The NBPT solution was added to the solidPergopak® M over a 42-minute period. The mixer speed was increased tosetting #2 after 27 minutes to help break up small aggregates. The bowlwas rotated by mechanically using an electric motor during the additionof the NBPT solution to facilitate mixing. The mixture was stirred foran additional 8 minutes at a mixer speed setting #6 to break up lumps.The final weight of Pergopak® M loaded with the NBPT solution was 83.3grams of a fine white free flowing powder.

Example 6 Pergopak® M Loading Using a 45.8 wt. % Solution of NBPT(N-n-butylthiophosphoric Triamide) in THF (Tetrahydrofuran)

Inside a fume hood 30.3 grams of Pergopak® M was weighed into astainless steel mixing bowl. Into a 250 ml addition funnel was weighed163.3 grams of the 45.8 wt. % solution of NBPT in THF. A section ofTygon® tubing was added to the additional funnel to allow for the dropwise addition of the NBPT solution onto the Pergopak® M. The mixer wasturn on to speed setting #1. The NBPT solution was added to the solidPergopak® M over a 39-minute period. The bowl was rotated bymechanically using an electric motor during the addition of the NBPTsolution to facilitate mixing. The mixture was stirred for an additional25 minutes at a mixer speed setting #2 to break up lumps. The finalweight of the Pergopak® M loaded with the NBPT solution was 107.3 gramsof a fine white free flowing powder.

Example 7 Pergopak® M Loading Using a 45.8 wt. % Solution of NBPT(N-n-butylthiophosphoric Triamide) in THF (Tetrahydrofuran)

Into a 1 liter round bottom flask containing 4 internal baffles wasweighed 20.6 grams of Pergopak® M. Into a 100 ml graduated cylinder wasweighed 77.5 grams of the 45.8 wt. % solution of NBPT in THF and 25.0grams of pure THF. The flask was attached to a solvent evaporator (BuchiRotavapor®) and evacuated to a pressure of 26 inch of vacuum. The flaskwas rotated at a slow speed so as to tumble the solid Pergopak® M. Abouthalf of the NBPT solution was vacuum transferred onto the Pergopak® Mover a 25-minute period at room temperature. The vacuum was thenincreased to 28 inches and the flask lowered into a warm water bath at30-35° C. The remaining NBPT solution was slowly added over a 75-minuteperiod. After an additional 14 minutes of mixing the flask was removedfrom the Rotavapor® and transferred into an open pan and allowed to airdry in a fume hood overnight. The final weight of the Pergopak® M loadedwith the NBPT solution was 66.2 grams of a fine white free flowingpowder.

Example 8 Pergopak® M Loading Using a 45.8 wt. % Solution of NBPT(N-n-butylthiophosphoric Triamide) in THF (Tetrahydrofuran)

Into a 1 liter round bottom flask containing 4 internal baffles wasweighed 25.8 grams of Pergopak® M. Into a 250 ml beaker was weighed126.2 grams of the 45.8 wt. % solution of NBPT in THF. The followingloading procedure was used: (1) Approximately 25 grams of the NBPTsolution was added to the Pergopak® M using a plastic pipette. (2) Theflask was attached to a solvent evaporator (Buchi Rotavapor®) androtated for 30-60 minutes at a slow speed so as to tumble the solidPergopak® M. (3) The flask was then put under full vacuum and loweredinto a warm water bath at 45C for 15-50 minutes. The flask was thenremoved from the Rotavapor® and steps (1) through (3) were repeateduntil all of the NBPT solution had been loaded. The final weight of thePergopak® M loaded with the NBPT solution was 86.2 grams of a fine whitepowder containing some agglomerates.

Example 9 Storage Stability of Pergopak® M Loaded with NBPT in thePresence and Absence of NMP

Pergopak® M loaded with NBPT from examples 1 through 6 were stored inclosed glass jars at room temperature for 8 months. During this study itwas observed that the samples of Pergopak® M loaded with NBPT in thepresence of NMP (Examples 1, 2 & 3) became clumpy and discolored overtime while the samples of Pergopak® M loaded without the use of NMP(Examples 4, 5 & 6) remained white and free flowing. The NBPT content ofthe samples was by HPLC analysis over time. The results are given in thetable below:

Assay at time Assay after 4 Assay after 8 % Loss after Sample No. zeromonths months 8 months Example 1 31.6 wt. % 26.7 wt. % 23.2 wt. % 26.6%Example 2 28.5 wt. % 23.3 wt. % 19.4 wt. % 31.9% Example 3 30.8 wt. %26.2 wt. % 21.1 wt. % 31.5% Example 4 61.0 wt. % 57.0 wt. % 54.2 wt. %11.1% Example 5 64.2 wt. % 58.3 wt. % 53.7 wt. % 16.4% Example 6 65.0wt. % 59.7 wt. % 56.6 wt. % 12.9%As the data shows the samples of this invention (Examples 4, 5 & 6) notonly had a loading level over twice the level of Examples 1 through 3but also had superior shelf life.

1. A process comprising depositing one or more active ingredients ontourea-formaldehyde polymers, wherein said one or more active ingredientsare selected from compounds, chemicals, etc., that find use inagricultural applications and said active ingredients are deposited ontosaid urea-formaldehyde polymers by contacting, in a drying device, aurea-formaldehyde polymer with a solution comprising a solvent selectedfrom ethers, alcohols, hydrocarbons, halogenated hydrocarbons andaromatic hydrocarbons and said one or more active ingredients underconditions including elevated temperatures and sub-atmosphericpressures.
 2. A process comprising contacting a urea-formaldehydepolymer with a solution comprising tetrahydrofuran and an activeingredient under conditions including elevated temperatures andsub-atmospheric pressures.
 3. The process according to any of claim 1 or2 wherein said active ingredient is selected from urease inhibitors,fungicides and insecticides.
 4. The process according to any of claim 1or 2 wherein said active ingredient is a urease inhibitor.
 5. Theprocess according to claim 4 wherein said urease inhibitor is NBPT. 6.The process according to any of claim 1 or 2 wherein saidurea-formaldehyde polymer is selected from those having a water contentof between from about 1 and 80 wt. %, based on the weight of theurea-formaldehyde polymer.
 7. The process according to claim 5 whereinsaid urea-formaldehyde polymer is selected from those having a watercontent of between from about 10 and 35 wt. %, based on the weight ofthe urea-formaldehyde polymer.
 8. The process according to any of claim1 or 2 wherein said urea-formaldehyde polymer is selected from i)PERGOPAK® ii) PERGOPAK® M urea-formaldehyde polymers.
 9. The processaccording to claim 7 wherein said urea-formaldehyde polymer is selectedfrom those sold under the name PERGOPAK® M by the Albemarle Corporation.10. The process according to claim 3 wherein said drying device isselected from high shear mixer, ribbon drier, blade drier, and othersimilar devices.
 11. The process according to claim 4 wherein saiddrying device is selected from ribbon driers and blade driers.
 12. Theprocess according to any of claim 1 or 2 wherein said urea-formaldehydepolymer and solution are introduced into the drying device i)simultaneously, ii) in stages, iii) either the polymer or solutionintroduced before the other, iv) or any combinations thereof.
 13. Theprocess according to claim 12 wherein said process is either batch orcontinuous.
 14. The process according to claim 10 wherein the solutionis introduced into the drying device after the urea-formaldehydepolymer.
 15. The process according to claim 12 wherein the introductionof the solution is at a rate substantially equal to the rate at whichthe solvent volatilizes.
 16. The process according to any of claim 1 or2 wherein said elevated temperatures are in the range of from about 20°C. to about 200° C. and said sub-atmospheric temperatures are in therange of from about 760 mmHg to about 0.1 mmHg.
 17. The processaccording to claim 8 wherein said elevated temperatures are in the rangeof from about 20° C. to about 100° C. and said sub-atmospherictemperatures are in the range of from about 500 mmHg to about 50 mmHg.18. The process according to claim 12 wherein said elevated temperaturesin the range of from about 20° C. to about 50° C. and saidsub-atmospheric temperatures are in the range of from about 100 mmHg toabout 50 mmHg.
 19. The coated urea-formaldehyde polymer of claim
 9. 20.An active-ingredient-coated urea-formaldehyde polymer having an activeingredient concentration greater than about 35 wt. %, based on theweight of the active-ingredient-coated urea-formaldehyde polymer,wherein said active ingredient is selected from urease inhibitors,fungicides and insecticides.
 21. An active-ingredient-coatedurea-formaldehyde polymer having an active ingredient concentrationgreater than about 35 wt. %, based on the weight of theactive-ingredient-coated urea-formaldehyde polymer, wherein said activeingredient is one or more of urease inhibitors, fungicides, andinsecticides, said active-ingredient-coated urea-formaldehyde polymermade by a) a process comprising depositing said active ingredient ontourea-formaldehyde polymers, wherein said active ingredient is depositedonto said urea-formaldehyde polymers by contacting, in a drying device,a urea-formaldehyde polymer with a solution comprising a solventselected from ethers, alcohols, hydrocarbons, halogenated hydrocarbonsand aromatic hydrocarbons and said active ingredient under conditionsincluding elevated temperatures and sub-atmospheric pressures therebyforming said active-ingredient-coated urea-formaldehyde polymer; or b) aprocess comprising contacting a urea-formaldehyde polymer with asolution comprising tetrahydrofuran and said active ingredient activeingredient under conditions including elevated temperatures andsub-atmospheric pressures thereby forming said active-ingredient-coatedurea-formaldehyde polymer.
 22. The active-ingredient-coatedurea-formaldehyde polymer according to claim 21 wherein said activeingredient is selected from urease inhibitors, fungicides andinsecticides.
 23. The active-ingredient-coated urea-formaldehyde polymeraccording to claim 21 wherein said active ingredient is a ureaseinhibitor.
 24. The active-ingredient-coated urea-formaldehyde polymeraccording to claim 21 wherein said urease inhibitor is NBPT.
 25. Theactive-ingredient-coated urea-formaldehyde polymer according to claim 22wherein the active ingredient concentration is in the range of fromabout 40 wt. % to about 80 wt. %, based on the weight of theactive-ingredient-coated urea-formaldehyde polymer.
 26. Theactive-ingredient-coated urea-formaldehyde polymer according to claim 21wherein the storage life of the active-ingredient-coatedurea-formaldehyde polymers is at least twice that ofactive-ingredient-coated urea-formaldehyde polymers that were coatedusing NMP as a solvent.
 27. The active-ingredient-coatedurea-formaldehyde polymer according to claim 25 wherein the storage lifeof the active-ingredient-coated urea-formaldehyde polymers is at leasttwice that of active-ingredient-coated urea-formaldehyde polymers thatwere coated using NMP as a solvent.
 28. The use of theactive-ingredient-coated urea-formaldehyde polymer according to claim 21in agricultural applications wherein the function of a urease inhibitoris desired.
 29. The use of the active-ingredient-coatedurea-formaldehyde polymer according to claim 27 in agriculturalapplications wherein the function of a urease inhibitor is desired.